Resurfacing Cylinder Head

[8SECONDSS]

47 Dodge Truck 218 cu. Flathead, overhauling engine and wanted to know if I should resurface the cylinder head. Was running perfect before the oiling problem. Thanks, Greg

[Scruffy49]

Have it checked for flatness, they can warp a bit when the head bolts are taken out. If it is flat, a deglazing pass will suffice.

[Dan Babb]

I remember reading that you can shave a bit off the head to boost compression and power a bit. Dont remember how much though. A search should turn up the info

Its basically free hp, so I would do it.

[8SECONDSS]

Will look into it.  Thanks for the replies. Greg

[Reg Evans]

Here's a milling chart to give you an idea of how much milling required to reach a certain compression ratio.

 

[8SECONDSS]

With shaving the head maybe .070 do yo think I would feel a difference in power? Thanks

[greg g]

You will feel a more responsive engine if not the feeling of more power.  I took .040 of my head and had the deck milled .010.  This on a 56 230 egine. This modification allows you to take advantage of todays higher octain fuels.  To go along with this the timing can be advanced about 5 degrees at idle which is probably where most of the feeling of quicker response comes from.  But in my opinion while the head is off you for the 30 to 40 buck it costs, it is probably the most bang for the buck you can get aside from dual exhaust and multiple carburetors. 

[8SECONDSS]

Thanks for the info. I'll try it out, Greg

[greg g]

The one caveat here is how do you know you are starting with a stock head??? I guess that is why most of us who cut ours use a bit a caution with how much to take off. Gotta make sure you are not going to jam valves into the head when you get it buttoned up. And I don't kow who if any one has the stock dimensions. So some work with your machine shop to determin how hgh the valvse are going and how deep your combustion chambers are a good idea before chucking it up inthe mill.

[Plymouthy Adams]

as milled head from the factory is what seems to be the only change in CR..yes knowing your orgin or present condition is paramount to milling and not ruining a good head or accidentally bend a few valves..if in doubt..CC the chambers

[Don Coatney]

A few years ago I found what I believe to be a virgin Chrysler head and measured it (as pictured below) prior to shaving it. I also used a dial indicator to measure actual valve lift after doing a re-grind on my cam to insure I would have ample valve to head clearance. I also took into consideration the thickness of a squished head gasket.

 

 

 

[DJ194950]

Q. Don,

Allowing for heat lenghting the valves, how much clearance do you think would be a minimun??

In the past i've read some mag. articles on hot motor builds (all v-8's) that stated some minimum the builder allowed but i really don't recall any specificate # for that clearance.

Wondering if you got some info from your machinist?

 

Thanks,

 

Doug

[Don Coatney]

It was close to 10 years ago when I did my measuring and I dont recall the clearance numbers. But here is a link that may help.

 

http://midstateantiquestockcarclub.com/flat_heads3.html

[DJ194950]

Thanks Don.

If i'm reading this right, measure old head gasket thickness,add to the valve lift measurement, and compare to the depth of the head depth at the valve "pockets" of the head. By placing a straightedge accross the head at the valve pockets of the head, depth can be determined and amount of a head shave maximum could be determined to achieve at at least a .040-.050 extra clearance?

I suppose that the compression ratio would be unknown, but with proper timing adjustments, maximum ratio for these engines could be used without preignition.

Thanks for the info,

Doug

[greg g]

George Ashe has stated the believes you can take off .090 and still run 87 octane fuel, with out fear of spark kock.  Again this assumes a stock head.  But the combinatio of some off the head and some off the block still needs some measurment to assure vavles clearing and seaing properly.

[pat lehmann]

I measured mine with stock valve lift and only a couple thou off the head figuring with a .075" head gasket and I didn't have a ton of room. I wrote the figures down so I'll have to check tomorrow but I'm pretty sure I couldn't take .090" off the head.

.060" intake, .090" exhaust is kind of a common rule of thumb for valve to piston clearance on a steel rod engine. Obviously you can get things a little tighter in a flathead configuration.